JPH1194234A - Method for reducing adhesion of ash to boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of heat transmission efficiency or clogging due to adhesion of ash to the heating tube by adding a specified compound into fuel or combustion gas. SOLUTION: In a super heavy residual oil emulsion fired boiler 10, one kind or more selected from CaCO3 , Fe2 O3 and Na2 CO3 is employed as an additive for reducing adhesion of ash. It is added by 0.05-0.5 mol for 1 mol of V2 O5 contained in the ash of super heavy residual oil emulsion. It is added into fuel before combustion or into a temperature region where the temperature in the downstream of burner zone of furnace is lower than 800 deg.C. More specifically, the temperature region for adding the additive extends from the burner zone where fuel 11 and the air 12 are introduced to the part between the heating tubes 14, 15 and the additive 17 is added at the position 17, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the amount of ash adhering to a heat transfer tube such as a superheater tube and a reheater tube in a super heavy oil emulsion fuel fired boiler.

[0002]

2. Description of the Related Art In recent years, fuel diversification has been studied in thermal power plants and the like, and various types of super heavy oil emulsion fuels represented by Orimulsion (registered trademark) have been used. Orimulsion is an emulsified fuel obtained by mixing about 30% by weight of water and a small amount of a surfactant with orinoco tar, an ultra-heavy oil, which is abundantly buried in the Orinoco River basin in Venezuela, South America. These ultra-heavy oil emulsion fuels are cheaper than heavy crude oil but have more ash, so in super-heavy oil emulsion fuel-fired boilers, ash adheres to heat transfer tubes such as superheater tubes and reheater tubes. Troubles such as a decrease in heat transfer efficiency and clogging occur, and this is a major problem of the boiler burning an ultra heavy oil emulsion fuel.

As a countermeasure, countermeasures such as strengthening of a suit blower, which is an ash removing device, addition of a Mg compound having a corrosion preventing and ash removing effect to a fuel, and the like are taken. But,
In the case of ultra-heavy oil emulsion fuel, the adhesion ash trouble is not solved even if the Mg compound having the ash removal effect is sufficiently added, and at present, it is mainly dealt with by strengthening the suit blower which is a ash removal device, It is still a major problem in boiler operation.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has been found to cause problems such as a decrease in heat transfer efficiency or blockage due to ash adhering to a heat transfer tube or the like in a super heavy oil emulsion fuel fired boiler. It is an object of the present invention to provide a method for reducing the attached ash of a boiler which can prevent the occurrence of ash.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the properties of the attached ash in a super heavy oil emulsion fuel-fired boiler. It has been found that the amount of attached ash can be reduced by adding a compound, and the present invention has been completed.

That is, according to the present invention, when burning a super heavy oil emulsion fuel in a super heavy oil emulsion fuel fired boiler, the gas temperature in the fuel and / or from the furnace burner zone to the temperature range of the gas downstream of 800 ° C.
₃ , an additive comprising at least one selected from the group consisting of Fe ₂ O ₃ and Na ₂ CO ₃ is added in an amount of 0.05 to 1 mol per mol of V ₂ O ₅ contained in the combustion ash of the super heavy oil emulsion fuel.
This is a method for reducing the attached ash of a boiler, characterized by adding at a ratio of 0.5 mol.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention reduces
CaCO as an additive for_Three, Fe_TwoO_ThreeAnd Na_TwoC
O_ThreeCharacterized by adding at least one selected from the group consisting of
I do. The amount of additive added is
V contained in combustion ash_TwoO_Five0.05 to 1 mole
The range is 0.5 mol. If the amount added is less than 0.05 mol
Has a small effect of addition and adheres if it exceeds 0.5 mol.
It is not preferable because the amount may increase. This means
In FIG. 3, FIG. 4, and FIG. _TwoO_Fiveof
When the molar ratio is 0.6 or more, ash adhesion tends to increase
This is true from a certain point.

The above-mentioned additive is added to the fuel before combustion, or is added to a temperature range where the gas temperature downstream from the furnace burner zone is up to 800 ° C. The reason for this is that ash adhesion is a problem mainly when the gas temperature is 7
The range is from 00 to 800 ° C., because the additive needs to be added to the upstream side. FIG. 1 shows an example of the temperature distribution in the boiler. In the boiler 10 shown in FIG.
1 and a portion between the burner zone into which the air 12 is introduced and a portion between the heat exchanger tubes 14 and 15 is a temperature range in which the additive in the present invention is added.
What is necessary is just to add from position 7. In FIG. 1, reference numerals 13 and 16 denote heat transfer tubes, respectively.

[0009]

EXAMPLES The method of the present invention will be described more specifically with reference to the following examples. (Example) As a guide for evaluating the easiness of adhesion of combustion ash to a heat transfer tube of a boiler, a combustion ash obtained by adding and mixing a predetermined amount of an additive on a sample table made of the same material as a heat transfer tube is used. Was placed on the sample, and the adhesion was measured after maintaining the same atmosphere and temperature in the boiler for a predetermined time. According to the experimental results of the present inventors, it has been confirmed that the amount of ash adhesion can be estimated from the ash adhesion (shearing force) thus measured.

As a sample of combustion ash, the composition shown in Table 1 was used.
A predetermined amount of CaCO ₃ , Fe ₂ O ₃ is used by using attached ash of orimulsion which is a typical heavy oil emulsion fuel.
Alternatively, the adhesive force to which Na ₂ CO ₃ was added was measured by using an ash adhesive force measuring device having a configuration shown in FIG. 2 described below while changing the temperature in a gas atmosphere having the composition shown in Table 2.
The ash adhesion force was determined by measuring the shearing force at the portion where the molded body of ash adhered to the sample stage by the method described later, and evaluating the shearing force ratio based on a shearing force of 300 g / cm ² (1.0). The measurement results are shown in FIGS. 3, 4, and 5. When the relationship between the test temperature and the ash adhesion is plotted again for the example of FIG. 5 in which Na ₂ CO ₃ is added, the result is as shown in FIG. Although not shown, the same tendency applies to FIGS. The following can be understood from these results. If 0.05 to 0.5 mol of CaCO ₃ , Fe ₂ O ₃ or Na ₂ CO ₃ is added to 1 mol of V ₂ O _{5 in the} orimulsion adhering ash to the orimulsion adhering ash, Adhesion decreases. The adhesive force of the orimulsion ash increases with increasing temperature up to about 750 ° C., but rapidly decreases at high temperatures of 800 ° C. or higher. Therefore, CaCO _{3 to be} added,
It is desirable to add Fe ₂ O ₃ and Na ₂ CO ₃ in the fuel or / and in a temperature range where the gas temperature downstream from the furnace burner zone is up to 800 ° C.

[0011]

[Table 1]

[0012]

[Table 2]

FIG. 2 shows a system diagram of an ash adhesion measuring device developed by the present inventors and used to evaluate the ash adhesion in the present embodiment, which measures the adhesion of the attached ash at a high temperature. FIG.
In the figure, 1 is a tubular electric furnace, and 2 is a porcelain reaction tube, which is installed in the tubular electric furnace 1. 2S and 2M are stoppers attached to both ends of the porcelain reaction tube 2, 2S is fixed and 2M is movable. Reference numeral 3 denotes a temperature controller, and 3S denotes a thermocouple for the temperature controller disposed on the fixed stopper 2S. 4
Is a temperature recorder, and 4S is a thermocouple for the temperature recorder arranged on the movable stopper 2M. Reference numeral 5 denotes a test gas cylinder which is a fixed stopper 2S via a 5B valve and a 5R flow meter.
Is connected by a test gas line 5L. Further, one test gas line 5L is connected to the movable stopper 2M, and is thereby exhausted outdoors. Reference numeral 6 denotes a sample stage, which is attached to the movable stopper 2M. Reference numeral 6A denotes a test ash, on which the test ash 6A is formed. Reference numeral 7 denotes an adhesive force measuring device, the tip of which is connected to a test ash press fitting 7E via a 7P push rod.

Using the ash adhesion measuring device having such a configuration, the adhesion of the orimulsion ash at a high temperature was measured, and the adhesion of the orimulsion ash under various conditions such as temperature, ash composition, and gas atmosphere was evaluated. The evaluation procedure is as follows. 1) The temperature of the tubular electric furnace 1 is set to the test temperature by the temperature controller 3, and the temperature is recorded on the temperature recorder 4. 2) The test gas is supplied from the test gas cylinders 5 to 5B valves,
It is introduced into the porcelain reaction tube 2 by a test gas line 5L via a 5R flow meter, and exhausted from the other test gas line 5L to the outside. 3) Next, the movable stopper 2M is removed, and the test ash 6A is formed and mounted on the sample stand 6 outside the porcelain reaction tube 2 using a forming device. In this test, a cylindrical molded body having a diameter of 14 mm and a height of 14 mm was used. 4) Set the movable stopper 2M in the porcelain reaction tube 2, monitor the temperature recorder 4, and wait until the temperature reaches the test temperature. 5) When the temperature reaches the test temperature, the test ash is allowed to stand for 30 minutes (usually: 30 minutes), and thereafter, the push rod 7P is moved and the test ash 6A is pushed by the test ash press 7E. 6) The force at which the test ash press 7E moves and shears the sample table 6 and the test ash 6A sintered at a high temperature is measured by the adhesive force measuring device 7.

[0015]

According to the method of the present invention, it is possible to reduce the adhesive force of the adhered ash during the combustion of the super heavy oil emulsion fuel at a high temperature, and to remove the adhered ash in the super heavy oil emulsion fuel fired boiler. It can be easily removed by a suit blower, which is an ash device, and major problems in boiler operation can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a temperature distribution in a boiler.

FIG. 2 is a system diagram of an ash adhesion measuring device for measuring the adhesion of attached ash at a high temperature used in Examples.

FIG. 3 is a graph showing the relationship between the CaCO ₃ / V ₂ O ₅ molar ratio and the ash adhesion measured in the examples.

FIG. 4 is a graph showing the relationship between the Fe ₂ O ₃ / V ₂ O ₅ molar ratio and ash adhesion measured in the examples.

FIG. 5 is a graph showing the relationship between the molar ratio of Na ₂ CO ₃ / V ₂ O ₅ and the ash adhesion measured in the examples.

FIG. 6 is a graph in which FIG. 5 is replotted with respect to the relationship between test temperature and ash adhesion.

Claims (1)

[Claims] Claims 1. An ultra-heavy oil emulsion fuel-fired boiler
In burning ultra-heavy oil emulsion fuel in
Gas temperature in fuel and / or downstream from furnace burner zone
In the temperature range up to 800 ° C, CaCO_Three, Fe_TwoO_ThreePassing
And Na_TwoCO _ThreeAddition of one or more selected from
Contained in the combustion ash of ultra heavy oil emulsion fuel
V_TwoO_Five0.05 to 0.5 mole per mole
A method for reducing adhering ash of a boiler, characterized by adding.